I propose a set of changes to the JavaFX property system that I've outlined in this PR: https://github.com/openjdk/jfx/pull/590
The changes fall into two categories: enforcement of correct usage (there are several cases listed in the PR), and deprecating untyped APIs (for removal in a future version) so as to make the intent of the API more clear to developers. Even though there are breaking changes, the impact on application code should be minimal. I'd welcome any comments on this proposal.